Voltage breakdown uniformity in piezoelectric structure for piezoelectric devices

ABSTRACT

In some embodiments, the present disclosure relates to a processing tool that includes a wafer chuck disposed within a hot plate chamber and having an upper surface configured to hold a semiconductor wafer. A heating element is disposed within the wafer chuck and configured to increase a temperature of the wafer chuck. A motor is coupled to the wafer chuck and configured to rotate the wafer chuck around an axis of rotation extending through the upper surface of the wafer chuck. The processing tool further includes control circuitry coupled to the motor and configured to operate the motor to rotate the wafer chuck while the temperature of the wafer chuck is increased to form a piezoelectric layer from a sol-gel solution layer on the semiconductor wafer.

BACKGROUND

Piezoelectric devices (e.g., piezoelectric actuators, piezoelectricsensors, etc.) are used in many modern day electronic devices (e.g.,automotive sensors/actuators, aerospace sensors/actuators, etc.). Oneexample of a piezoelectric device is a piezoelectric actuator. Apiezoelectric actuator can be utilized to create a physical movementthat exerts a force on a physical part in a system under the control ofan electrical signal. The physical movement generated by thepiezoelectric actuator can be utilized to control various kinds ofsystems (e.g., mechanical systems, optical systems, etc.).

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a cross-sectional view of some embodiments ofpiezoelectric device comprising a piezoelectric structure formed to havea substantially uniform breakdown voltage throughout the piezoelectricstructure.

FIG. 2 illustrates a top-view of some embodiments of a wafer comprisingmultiple die regions, wherein each die comprises a piezoelectricstructure having a certain breakdown voltage.

FIG. 3 illustrates a cross-sectional view of some embodiments of aspin-coat tool comprising an orientor device used to form apiezoelectric structure with a small variation in breakdown voltage.

FIG. 4 illustrates a perspective view of some embodiments of a hot platechamber comprising an orientor device used to form a piezoelectricstructure with a small variation in breakdown voltage.

FIG. 5 illustrates a perspective view of some embodiments of multiplehot plate chambers in a hot plate tool, wherein each hot plate chambercomprises an orientor device used to form a piezoelectric structure witha small variation in breakdown voltage.

FIG. 6 illustrates a cross-sectional view of some embodiments of a hotplate chamber comprising a rotational device configured to rotate a hotplate during baking processes to reduce variation in breakdown voltageof a piezoelectric structure.

FIG. 7 illustrates a cross-sectional view of some embodiments ofmultiple hot plate chambers in a hot plate tool, wherein each hot platechamber comprises a rotational device configured to rotate a hot plateduring baking processes to reduce variation in breakdown voltage of apiezoelectric structure.

FIGS. 8-18 illustrate various views of some embodiments of a method offorming a piezoelectric structure over a wafer using a hot plate chambercomprising a motor configured to rotate a hot plate during bakingprocesses to reduce variation in breakdown voltage of the piezoelectricstructure.

FIG. 19 illustrates a flow diagram of some embodiments corresponding tothe method of FIGS. 8-18 .

FIGS. 20A-23 illustrate various views of some other embodiments ofmethod of forming a piezoelectric structure over a wafer using a hotplate chamber comprising an orientor device used to form thepiezoelectric structure with a small variation in breakdown voltage.

FIG. 24 illustrates a flow diagram of some embodiments corresponding tothe method of FIGS. 20A-23 .

FIGS. 25A-28 illustrate various views of yet some other embodiments of amethod of forming a piezoelectric structure over a wafer using aspin-coat tool comprising an orientor device used to form thepiezoelectric structure with a small variation in breakdown voltage.

FIG. 29 illustrates a flow diagram of some embodiments corresponding tothe method of FIGS. 25A-28 .

FIGS. 30-32 illustrate various views of some embodiments of forming atop electrode over a piezoelectric structure on a wafer to form multiplepiezoelectric devices.

FIG. 33 illustrates a flow diagram of some embodiments of a method offorming piezoelectric devices by rotating a wafer during a bakingprocess to form a piezoelectric structure in order to reduce variationbreakdown voltages of the piezoelectric structures in the piezoelectricdevices.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

A piezoelectric device is a metal-insulator-metal (MIM) device thatincludes a piezoelectric structure arranged between top and bottomelectrodes. When a sufficient voltage bias is applied across the top andbottom electrodes, a mechanical strain may be induced in thepiezoelectric structure. The mechanical strain may, for example, be usedin acoustical, mechanical, and/or optical applications. The change inthe structure of the piezoelectric layer may affect other electronicproperties in the piezoelectric structure such as permittivity,capacitance, and polarization. The change in structure of thepiezoelectric structure is a reversible process when the voltage biasesapplied to the piezoelectric structure are less than a breakdown voltageof the piezoelectric layer. If a voltage bias greater than or equal tothe breakdown voltage of the piezoelectric structure is applied to thepiezoelectric layer, the mechanical strain induced in the piezoelectriclayer is irreversible, and thus, the piezoelectric structure is damagedcausing the piezoelectric device to be unreliable.

In some methods of manufacturing a piezoelectric device, a bottomelectrode may be formed over a wafer; a piezoelectric structure may beformed over the bottom electrode; and a top electrode may be formed overthe piezoelectric structure. Then, a dicing process may be performedalong die regions on the wafer to form many piezoelectric devices fromthe wafer. In some embodiments, a sol-gel process is used to form thepiezoelectric structure on the wafer. The sol-gel process may include aspin-coat step, wherein a sol-gel solution layer is formed over thewafer and a baking process, wherein drying, decomposition, anddensification occur to form a solid, piezoelectric structure from thesol-gel solution layer. However, in some embodiments, the removal ofgases during the baking process is not uniform throughout thepiezoelectric structure, leading to varying piezoelectric compositionsthroughout the piezoelectric structure, and ultimately leading to a widerange of breakdown voltages throughout the piezoelectric structure onthe wafer. For example, in some embodiments, a first piezoelectricdevice and a second piezoelectric device coming from a same wafer as thefirst piezoelectric device may have a difference in breakdown voltagefrom one another of up to 20 volts. As a result, the piezoelectricdevices formed from a same sol-gel process do not have predictableproperties (e.g., breakdown voltage, composition, etc.).

Various embodiments of the present disclosure relate to rotating thewafer to be at different orientations within a hot plate chamber duringthe baking process to increase the uniformity of the baking processthroughout the piezoelectric structure to reduce a variation incomposition throughout the piezoelectric structure and thus, to reducethe range of breakdown voltages in the final piezoelectric devicesformed from the piezoelectric structure. For example, in someembodiments, rotating the wafer to be at different orientations withinthe hot plate chamber during the baking process may reduce the range ofbreakdown voltages of the final piezoelectric devices by 50 percent. Insome embodiments of the present disclosure, rotation of the wafer may beachieved by rotating the wafer between different cycles of the bakingprocess using an orientor device, whereas in other embodiments of thepresent disclosure, the rotation of the wafer may be achieved bycontinuously rotating the wafer within the hot plate chamber during thebaking process using a rotatable wafer chuck or hot plate. As a result,the sol-gel process that includes performing a baking process atdifferent orientations in the hot plate chamber produces a piezoelectricstructure with a more uniform breakdown voltage distribution throughoutthe piezoelectric structure, thereby increasing reliability of theresulting piezoelectric devices.

FIG. 1 illustrates a cross-sectional view 100 of some embodiments of apiezoelectric device coupled to control circuitry.

The piezoelectric device in the cross-sectional view 100 may comprise,in some embodiments, a bottom electrode 106 arranged over a substrate102. A piezoelectric structure 108 may be arranged over the bottomelectrode 106 and beneath a top electrode 110. In some embodiments, apassivation layer 104 may be arranged directly between the substrate 102and the bottom electrode 106. In some embodiments, the bottom electrode106 may be wider than the top electrode 110 and the piezoelectricstructure 108. In some embodiments, the piezoelectric structure 108 maybe wider than the top electrode 110. In yet other embodiments, outersidewalls of the top electrode 110, the piezoelectric structure 108,and/or the bottom electrode 106 may be substantially aligned with oneanother. In some embodiments, the piezoelectric structure 108 maycomprise multiple layers of a same piezoelectric material. In someembodiments, the piezoelectric structure 108 may comprise, for example,a piezoelectric ceramic material such as lead zirconate titanate, whichcomprises lead, zirconium, titanium, and oxygen. In some otherembodiments, the piezoelectric structure 108 may comprise, for example,aluminum nitride, lithium niobate, gallium arsenide, zinc oxide, quartzsingle crystals, polymer-film piezoelectrics, or some other suitablepiezoelectric material. In some embodiments, the piezoelectric structure108 may have a thickness in a range of between, for example,approximately 2,000 angstroms and approximately 30,000 angstroms.

In some embodiments, control circuitry 112 may be coupled to the top andbottom electrodes 110, 106 through wires 111. In some embodiments,electrical contacts such as solder bumps or bond pads (not shown) couplethe wires 111 directly to the top and bottom electrodes 110, 106. Insome embodiments, the control circuitry 112 is configured to applyvoltage biases across the piezoelectric structure 108. In someembodiments, to prevent irreversible damage to the piezoelectricstructure 108, the control circuitry 112 is configured to apply voltagebiases that are less than a breakdown voltage of the piezoelectricstructure 108. Thus, by knowing the breakdown voltage of thepiezoelectric structure 108, the control circuitry 112 can preventdamage to the piezoelectric device.

In some embodiments, the piezoelectric structure 108 is formed over anentire wafer using a sol-gel process. In such embodiments, the wafer isthen diced to form the piezoelectric device in the cross-sectional view100. In such embodiments, the piezoelectric structure 108 may be formedover the wafer to have a reduced variation in composition throughout thepiezoelectric structure 108 by rotating the wafer during a bakingprocess of a sol-gel method. This way, the piezoelectric structure 108may undergo a more uniform baking process, and differences betweenbreakdown voltages amongst the resulting piezoelectric devices arereduced.

FIG. 2 illustrates a top-view 200 of some embodiments of a piezoelectricstructure arranged over a wafer and breakdown voltages of thepiezoelectric structure of each die region on the wafer. The top-view200 of FIG. 2 will be discussed below in conjunction with thecross-sectional view 100 of FIG. 1 .

In some embodiments, multiple die regions 218 are arranged on a wafer214, and a dicing process that utilizes a rotating blade and/or waterwill separate each die region 218 to form a piezoelectric deviceillustrated in FIG. 1 . Thus, multiple piezoelectric devices may beformed on a single wafer 214 to increase manufacturing efficiency.

The top-view 200 of FIG. 2 illustrates the piezoelectric structure 108arranged over the wafer 214. The substrate 102 of FIG. 1 corresponds toa portion of the wafer 214. In some embodiments, the bottom electrode106 and the passivation layer 104 may be arranged behind thepiezoelectric structure 108 in FIG. 2 . Further, in some embodiments,the top electrode 110 may be formed over the piezoelectric structure 108prior to performing a dicing process.

In some embodiments, each die region 218 that corresponds to apiezoelectric device has a breakdown voltage that corresponds to a lowbreakdown voltage 204, a mid-breakdown voltage 206, or a high breakdownvoltage 208 as indicated by a diagonal-stripe pattern, a cross pattern,or a concentric-circle pattern, respectively. For example, in someembodiments, according to a legend 202 in FIG. 2 , die regions 218having the low breakdown voltage 204 have a breakdown voltage in a rangeof between a and b; die regions 218 having the mid-breakdown voltage 206have a breakdown voltage in a range of between b and c; and die regions218 having the high breakdown voltage 208 have a breakdown voltage in arange of between c and d. In such embodiments, a may be equal to aminimum breakdown voltage of the piezoelectric structure 108, and d maybe equal to a maximum breakdown voltage of the piezoelectric structure108. In some embodiments, the minimum breakdown voltage of thepiezoelectric structure 108, or a, may be in a range of between, forexample, approximately 60 volts and approximately 62 volts. In someembodiments, the maximum breakdown voltage of the piezoelectricstructure 108, or d, may be in a range of between, for example,approximately 68 volts and approximately 70 volts. In some otherembodiments, the maximum breakdown voltage of the piezoelectricstructure 108, or d, may be greater than 80 volts, for example.

Thus, in some embodiments, an overall variation in the breakdownvoltages throughout the piezoelectric structure 108 on the wafer 214 maybe quantified by a range of between a and d. In some embodiments, thedifference between a and d is in a range of between, for exampleapproximately 1 volt and approximately 8 volts. In some otherembodiments, the difference between a and d is in a range of between,for example, approximately 8 volts and approximately 10 volts. Thereliability of the piezoelectric structure 108 may be increased byreducing the range between a and d such that the piezoelectric structure108 may be formed with a more uniform, and thus, predictable breakdownvoltage for each die region 218. This way, each piezoelectric device hasa known breakdown voltage such that the control circuitry 112 does notapply a voltage bias across the piezoelectric structure 108 in apiezoelectric device that exceeds the known breakdown voltage andirreversibly damage the piezoelectric structure 108.

In some embodiments, reducing the range between a and d for thebreakdown voltage of the piezoelectric structure 108 is achieved byrotating the wafer 214 during the baking process of a sol-gel processused to form the piezoelectric structure 108. In some embodiments, theorientation of the wafer 214 is determined by identifying a notch 216 inthe wafer 214. Then, in such embodiments, an orientor device can rotatethe wafer 214 such that the notch 216 is in a first predeterminedposition with respect to a hot plate chamber during a first cycle of thebaking process. In such embodiments, after the first cycle of the bakingprocess, the orientor device may rotate the wafer 214 by a predeterminedamount of degrees to a second predetermined position, and then, a secondcycle of the baking process may be performed. In such embodiments, thenumber of cycles of the baking process may correspond to 360 degreesdivided by the predetermined amount of degrees. For example, in someembodiments, the predetermined amount of degrees is equal to 90 degrees,and thus, the baking process comprises four cycles.

FIG. 3 illustrates a cross-sectional view 300 of some embodiments of aspin-coat tool for a sol-gel process and comprising an orientor device.

In some embodiments, a spin-coat tool housing 316 defines the spin-coattool. In some embodiments, a rotatable shaft 302 is arranged on thebottom of the spin-coat tool housing 316, and a wafer chuck 304 iscoupled to a top of the rotatable shaft 302. In such embodiments, thewafer chuck 304 may be configured to hold a wafer 214. In someembodiments, the spin-coat tool further comprises a solution housing 306and nozzle 308 used to deposit a sol-gel solution onto the wafer 214during a spin-coating step of a sol-gel process. In some embodiments,the solution housing 306 and nozzle 308 are arranged directly over thewafer chuck 304. In other embodiments, some other sol-gel solutiondistribution apparatus may be used instead of the solution housing 306and the nozzle 308, such as a cup, a syringe, or the like.

In some embodiments, the rotatable shaft 302 and/or the solution housing306 and nozzle 308 are controlled by spin coat control circuitry 318.The spin coat control circuitry 318 is arranged within the spin-coattool housing 316 in some embodiments, whereas in other embodiments, thespin coat control circuitry 318 may be arranged outside of the spin-coattool housing 316. In some embodiments, the spin coat control circuitry318 is directly coupled to the rotatable shaft 302 and/or the solutionhousing 306 and nozzle 308 through wires 317, whereas in otherembodiments, the spin coat control circuitry 318 is coupled to therotatable shaft 302 and/or the solution housing 306 and nozzle 308wirelessly. Nevertheless, in some embodiments, the spin coat controlcircuitry 318 is configured to rotate 303 the rotatable shaft 302 toevenly distribute a sol-gel solution (not shown) onto the wafer 214.Thus, after the spin-coat process, the sol-gel solution is arranged overthe wafer 214 as a layer with a substantially uniform thickness.

In some embodiments, the spin-coat tool further comprises an orientordevice 310. In some embodiments, the orientor device 310 is arrangedwithin the spin-coat tool housing 316. In such embodiments, the orientordevice 310 may comprise some type of optical image device such as, forexample, a charge-coupled device (CCD) image sensor, a complementarymetal oxide semiconductor (CMOS) image sensor, a time of flight (ToF)camera, or some other optical image device. In some embodiments, theorientor device 310 may be configured to use the optical image device tolocate the notch (216 of FIG. 2 ) on the wafer 214 after the sol-gelsolution is distributed on the wafer 214. Thus, in some embodiments, theorientor device 310 may be configured to optically analyze an entirearea of the wafer 214, as illustrated by dotted lines 314. In someembodiments, the orientor device 310 is coupled to orientor controlcircuitry 312. The orientor control circuitry 312 is arranged within thespin-coat tool housing 316 in some embodiments, whereas in otherembodiments, the orientor control circuitry 312 may be arranged outsideof the spin-coat tool housing 316. In some embodiments, the orientorcontrol circuitry 312 is directly coupled to the orientor device 310through wires 319, whereas in other embodiments, the orientor controlcircuitry 312 may be coupled to the orientor device 310 wirelessly.Nevertheless, in some embodiments, the orientor control circuitry 312may turn the orientor device 310 “ON” after the spin coat controlcircuitry 318 is turned “OFF” to locate the notch (216 of FIG. 2 ) onthe wafer 214 after the sol-gel solution has been deposited on the wafer214.

In some embodiments, the orientor device 310 further comprises analignment device that is configured to orient the wafer 214 such thatthe notch (216 of FIG. 2 ) is arranged at a specific location on thewafer chuck 304. In such embodiments, the alignment device of theorientor device 310 may be or comprise a rotational feature on the waferchuck 304, a robotic arm, or some other apparatus configured to move thewafer 214. In other embodiments, the alignment device of the orientordevice 310 may be arranged outside of the spin-coat tool housing 316. Insome embodiments, the orientor device 310 may be also be known as awafer alignment system. Overall, the orientor device 310 may beconfigured to transport the wafer 214 at a certain orientation accordingto the notch (216 of FIG. 2 ) location into the next processing chamberof the sol-gel process.

FIG. 4 illustrates a perspective view 400 of some embodiments of a hotplate chamber for a sol-gel process and comprising an orientor device.

In some embodiments, a hot plate chamber 404 defined by hot platechamber housing is used in a sol-gel process and configured to perform abaking process on a sol-gel solution layer. The baking process maycomprise multiple cycles and/or temperature conditions to dry,decompose, and densify the sol-gel solution layer to form a solid layerover the wafer 214. In some embodiments, the hot plate chamber 404 isarranged in a structural housing 402 and held in the structural housing402 by hot plate holder structures 406. A hot plate 408 is arranged on abottom of the hot plate chamber 404, and in some embodiments, the hotplate chamber 404 may be opened 414 using a door 416 to load a wafer 214onto the hot plate 408. In some embodiments, the hot plate 408 comprisesa wafer chuck configured to hold the wafer 214 at an upper surface ofthe wafer chuck and a heating element configured to increase atemperature of the wafer chuck.

The hot plate 408 is configured to provide heat in the hot plate chamber404 to facilitate the baking process. The hot plate 408 may becontrolled by hot plate chamber control circuitry 420. The hot platechamber control circuitry 420 is arranged within the hot plate chamber404 in some embodiments, whereas in other embodiments, the hot platechamber control circuitry 420 may be arranged outside of the hot platechamber 404. In some embodiments, the hot plate chamber controlcircuitry 420 is directly coupled to the hot plate chamber 404 and/orhot plate 408 through wires 418, whereas in other embodiments, the hotplate chamber control circuitry 420 may be coupled to the hot platechamber 404 and/or the hot plate 408 wirelessly. The hot plate chambercontrol circuitry 420 may, in some embodiments, be configured to controlthe temperature settings, door 416, and/or other parameters of the hotplate chamber 404.

In some embodiments, during the baking process, gases are released fromthe sol-gel solution layer on the wafer 214. Thus, in some embodiments,the hot plate chamber 404 may comprise gas pore openings 412, whereinthe gas pore openings 412 extend through the hot plate chamber 404 andare coupled to gas exhaust lines 410. Thus, in some embodiments, thegases, such as, for example, carbon dioxide, water vapor, oxygen, or thelike, released during the baking process may exit the hot plate chamber404 through the gas pore openings 412 and the gas exhaust lines 410. Insome embodiments, the gas exhaust lines 410 may be fixed to thestructural housing 402. Further, in some embodiments, there may be moreor less than four gas pore openings 412 arranged within the hot platechamber 404. In some embodiments, the gas pore openings 412 do notcompletely surround the hot plate 408. For example, in some embodiments,the gas pore openings 412 may not be arranged on the door 416 of the hotplate chamber 404. In such embodiments, the rate of removal of gasesthrough the gas pore openings 412 from certain areas of the wafer 214may be quicker than other areas of the wafer 214.

Therefore, in some embodiments, to more evenly remove gases during thebaking process and result in a more uniform composition throughout thesolid layer that is formed on the wafer 214, the hot plate chamber 404may further comprise the orientor device 310 coupled to orientor controlcircuitry 312. In some embodiments, the orientor device 310 may bearranged near a top of the hot plate chamber 404. In such embodiments,the orientor device 310 may comprise an optical imaging device and analignment device in order to rotate the wafer 214 to be at differentorientations with respect to the hot plate chamber 404 throughout thebaking process. In some embodiments, for example, the optical imagedevice (e.g., CCD image sensor, CMOS image sensor, ToF camera, etc.) ofthe orientor device 310 may be configured to locate the notch (216 ofFIG. 2 ) on the wafer 214, and the alignment device (e.g., rotationalfeature, robotic arm, etc.) of the orientor device 310 may be configuredto move the wafer 214 such that the notch (216 of FIG. 2 ) is located ata predetermined position within the hot plate chamber 404 on the hotplate 408. For example, in some embodiments, a first cycle of the bakingprocess is performed while the wafer 214 is at a first predeterminedposition in the hot plate chamber 404; a second cycle of the bakingprocess is performed while the wafer 214 is at a second predeterminedposition in the hot plate chamber 404; a third cycle of the bakingprocess is performed while the wafer 214 is at a third predeterminedposition in the hot plate chamber 404; and a fourth cycle of the bakingprocess is performed while the wafer 214 is at a fourth predeterminedposition in the hot plate chamber 404.

Thus, as the wafer is moved or rotated between cycles of the bakingprocess, the removal of gases through the gas pore openings 412 may bemore uniform throughout all areas of the wafer 214. As a result, thesolid layer (e.g., the piezoelectric structure 108 of FIG. 1 ) formedfrom the sol-gel solution layer may have a more uniform composition andthus, a smaller variation in properties (e.g., breakdown voltage)throughout the solid layer (e.g., the piezoelectric structure 108 ofFIG. 1 ).

FIG. 5 illustrates a perspective view 500 of some embodiments ofmultiple hot plate chambers comprising orientor devices that arevertically stacked to increase manufacturing efficiency.

The perspective view 500 includes a first hot plate chamber 404 a, asecond hot plate chamber 404 b, a third hot plate chamber 404 c, and afourth hot plate chamber 404 d vertically arranged in the structuralhousing 402. Thus, multiple wafers (214 of FIG. 4 ) may besimultaneously processed, thereby increasing the manufacturingefficiency. In such embodiments, each of the first through fourth hotplate chambers 404 a-d may comprise an orientor device 310. Further, insome embodiments, each of the first through fourth hot plate chamber 404a-d and each orientor device 310 within each of the first through fourthhot plate chambers 410 a-d may comprise its own control circuitry. Forexample, in some embodiments, the first hot plate chamber 404 a and theorientor device 310 of the first hot plate chamber 404 a may be coupledto first hot plate chamber control circuitry 420 a and first orientorcontrol circuitry 312 a, respectively; the second hot plate chamber 404b and the orientor device 310 of the second hot plate chamber 404 b maybe coupled to second hot plate chamber control circuitry 420 b andsecond orientor control circuitry 312 b, respectively; the third hotplate chamber 404 c and the orientor device 310 of the third hot platechamber 404 c may be coupled to third hot plate chamber controlcircuitry 420 c third orientor control circuitry 312 c, respectively;and the fourth hot plate chamber 404 d and the orientor device 310 ofthe fourth hot plate chamber 404 d may be coupled to fourth hot platechamber control circuitry 420 d and fourth orientor control circuitry312 d, respectively. In other embodiments, the first through fourth hotplate chambers 410 a-d and corresponding orientor devices 310 may beoperated by a single hot plate chamber control circuitry and orientorcontrol circuitry, respectively.

FIG. 6 illustrates a cross-sectional view 600 of some alternativeembodiments of a hot plate chamber used in a sol-gel process andcomprising a motor to continuously rotate a hot plate in the hot platechamber.

In some embodiments, the hot plate chamber 404 may comprise a motor 602or some suitable rotational device configured to rotate 604 the hotplate 408 around an axis of rotation 610 extending through and normal toan upper surface of the hot plate 408. In some embodiments, for example,the motor 602 may be or comprise an actuator. In some embodiments, thehot plate 408 and thus, also the wafer 214, may be continuously rotatedduring a baking process in the hot plate chamber 404. In someembodiments, the motor 602 may be coupled to and controlled by motorcontrol circuitry 606. In some embodiments, the motor control circuitry606 may be arranged within the hot plate chamber 404, whereas in otherembodiments, the motor control circuitry 606 may be arranged outside ofthe hot plate chamber 404. Further, in some embodiments, the motorcontrol circuitry 606 may be coupled to the motor 602 through wires 603,whereas in other embodiments, the motor control circuitry 606 may becoupled to the motor 602 wirelessly. The motor control circuitry 606 andthe motor 602 may be configured to rotate 604 the hot plate 408 a full360-degree rotation during the baking process at a constant speed (e.g.,rotations per minute) in some embodiments. In some embodiments, themotor control circuitry 606 and the motor 602 may be configured torotate 604 the hot plate 408 multiple, full 360-degree rotations duringthe baking process.

In some embodiments, the distribution of gases exiting the hot platechamber 404 through the gas pore openings 412 may be more eventhroughout the wafer 214 because of the wafer 214 is continuouslyrotating. As a result, the solid layer (e.g., the piezoelectricstructure 108 of FIG. 1 ) formed from the sol-gel solution layer mayhave a more uniform composition and thus, a smaller variation inproperties (e.g., breakdown voltage) throughout the solid layer (e.g.,the piezoelectric structure 108 of FIG. 1 ). Further, in someembodiments, wherein the hot plate chamber 404 comprises the motor 602,the baking process may comprise a single cycle, which increasesmanufacturing efficiency.

FIG. 7 illustrates a cross-sectional view 700 of some embodiments ofmultiple hot plate chambers comprising motors configured to continuouslyrotate the hot plates and that are vertically stacked to increasemanufacturing efficiency.

The cross-sectional view 700 includes a first hot plate chamber 404 a, asecond hot plate chamber 404 b, and a third hot plate chamber 404 cvertical arranged in the structural housing 402. Thus, multiple wafers(214 of FIG. 6 ) may be simultaneously processed, thereby increasingmanufacturing efficiency. It will be appreciated that in otherembodiments, there may be more or less than the three hot plate chambers(404 a-c) vertically arranged in the structural housing 402. In someembodiments, each of the first through third hot plate chambers 404 a-cmay comprise a motor 602 configured to rotate 604 the hot plate 408around the axis of rotation 610 during a baking process. In someembodiments, the first hot plate chamber 404 a and the motor 602 of thefirst hot plate chamber 404 a may be coupled to the first hot platechamber control circuitry 420 a and first motor control circuitry 606 a,respectively; the second hot plate chamber 404 b and the motor 602 ofthe second hot plate chamber 404 b may be coupled to the second hotplate chamber control circuitry 420 b and second motor control circuitry606 b, respectively; and the third hot plate chamber 404 c and the motor602 of the third hot plate chamber 404 c may be coupled to the third hotplate chamber control circuitry 420 c and third moto control circuitry606 c, respectively. In other embodiments, each of the first throughthird hot plate chambers 404 a-c and corresponding motors 602 may beoperated by a single hot plate control circuitry and motor controlcircuitry, respectively.

FIGS. 8-18 illustrate various views 800-1800 of some embodiments of amethod of forming a piezoelectric structure on a wafer by a sol-gelprocess using a continuously rotating hot plate. Although FIGS. 8-18 aredescribed in relation to a method, it will be appreciated that thestructures disclosed in FIGS. 8-18 are not limited to such a method, butinstead may stand alone as structures independent of the method.

As shown in cross-sectional view 800 of FIG. 8 , a wafer 214 isprovided. In some embodiments, the wafer 214 may be or comprise asemiconductor material. In some embodiments, the wafer 214 may compriseany type of semiconductor body (e.g., silicon/CMOS bulk, silicon,germanium, SiGe, SOI, etc.). In some embodiments, a passivation layer104 may be formed on the wafer 214. In some embodiments, the passivationlayer 104 may comprise titanium oxide, silicon dioxide, silicon nitride,or some other suitable passivation material. In some embodiments, thepassivation layer 104 may be formed by way of a deposition process(e.g., physical vapor deposition (PVD), chemical vapor deposition (CVD),plasma enhanced CVD (PE-CVD), atomic layer deposition (ALD), sputtering,etc.).

Further, in some embodiments, a bottom electrode 106 may be formed overthe wafer 214. In some embodiments, the bottom electrode 106 is formeddirectly on the passivation layer 104. In some embodiments, the bottomelectrode 106 may comprise, for example, copper, platinum, gold, silver,titanium, cobalt, titanium nitride, manganese, zinc, or some othersuitable conductive material. In some embodiments, the bottom electrode106 may be formed by way of a deposition process (e.g., PVD, CVD,PE-CVD, ALD, sputtering, etc.).

FIG. 9 illustrates a top-view 900 of some embodiments of thecross-sectional view 800 of FIG. 8 after the formation of the bottomelectrode 106.

As shown in the top-view 900 of FIG. 9 , in some embodiments, the wafer214 has a substantially circular shape from the top-view 900. However,in some embodiments, the wafer 214 comprises a notch 216 near an edge ofthe wafer 214. The notch 216 in the wafer 214 may be described as anindent in the wafer 214. In some embodiments, the notch 216 may have apointed profile like in the top-view of FIG. 9 , whereas in otherembodiments, the notch 216 may have a rounded profile. Nevertheless, thelocation of the notch 216 may be used in future processing steps toalign the wafer 214 in processing tools.

As shown in cross-sectional view 1000 of FIG. 10 , in some embodiments,the wafer 214 may be transported into a cooling chamber defined bycooling chamber housing 1004. In some embodiments, the cooling chamberhousing 1004 may comprise a wafer chuck 1002, wherein the wafer 214 isplaced on the wafer chuck 1002. In some embodiments, the wafer chuck1002 may also be a cooling plate, wherein the wafer chuck 1002 comprisesa cooling element configured to reduce a temperature of the wafer chuck1002. In some embodiments, the cooling chamber may cool the wafer 214and overlying layers (e.g., the passivation layer 104, the bottomelectrode 106) to a temperature in a range of between, for example,approximately 20 degrees Celsius and approximately 26 degrees Celsius.Thus, in some embodiments, the wafer 214 is inserted into the coolingchamber housing 1004 after the formation of the bottom electrode 106over the wafer 214 to reduce a temperature of the bottom electrode 106for future processing steps.

As shown in cross-sectional view 1100 of FIG. 11 , in some embodiments,the wafer 214 may be transported into a spin-coat tool defined byspin-coat tool housing 316. In such embodiments, the wafer 214 may beloaded onto a wafer chuck 304 coupled to a rotatable shaft 302. In someembodiments, the rotatable shaft 302 is coupled to spin coat controlcircuitry 318 through wires 317 or wirelessly. Further, in someembodiments, a solution housing 306 and nozzle 308 are arranged at a topof the spin-coat tool housing 316 and overlie the wafer 214.

As shown in cross-sectional view 1200 of FIG. 12 , in some embodiments,a sol-gel solution 2022 is deposited onto the wafer 214 from thesolution housing 306 and the nozzle 308. In some embodiments, thesol-gel solution 2022 comprises a colloidal solution when initiallydeposited on the bottom electrode 106. In some embodiments, the sol-gelsolution 2022 comprises, for example, lead, zirconium, and titaniumdispersed in one or more solvents. In such embodiments, the sol-gelsolution 2022 may be used to form a piezoelectric layer comprising leadzirconate titanate. In some embodiments, the one or more solvents maycomprise carbon, hydrogen, and/or oxygen. It will be appreciated that insome other embodiments, the sol-gel solution 1202 may comprise othermetals than lead, zirconium, and/or titanium dispersed in one or moresolvents to produce a piezoelectric layer other than lead zirconatetitanate.

As shown in cross-sectional view 1300 of FIG. 13 , in some embodiments,the spin coat control circuitry 318 turns the rotatable shaft 302 “ON”to rotate 303 the rotatable shaft 302, the wafer chuck 304, and thus,the wafer 214. In such embodiments, the sol-gel solution (1202 of FIG.12 ) is distributed evenly over the wafer 214 and the bottom electrode106 as a sol-gel solution layer 1302. In some embodiments, thedeposition of the sol-gel solution (1202 of FIG. 12 ) and the rotating303 of the wafer 214 in FIG. 13 are performed simultaneously, whereas inother embodiments, the sol-gel solution (1202 of FIG. 12 ) is deposited,and then, the rotatable shaft 302 is rotated 303. Nevertheless, thesteps in FIGS. 12 and 13 make up a spin-coat process in the sol-gelprocess in order to even distribute the sol-gel solution (1202 of FIG.12 ) into a sol-gel solution layer 1302 on the wafer 214.

As shown in perspective view 1400 of FIG. 14 , in some embodiments, thewafer 214 is transported into a hot plate chamber 404. In suchembodiments, a door 416 of the hot plate chamber 404 may be opened 414to load the wafer 214 onto a hot plate 408 within the hot plate chamber404. In some embodiments, the hot plate 408 may comprise a wafer chuckhaving an upper surface configured to hold the wafer 214 and may alsocomprise a heating element configured to increase a temperature of thewafer chuck, and thus, the wafer 214. In some embodiments, the hot platechamber 404 may be held in a structural housing 402 by hot plate holderstructures 406. In some embodiments, gas pore openings 412 may bearranged within the hot plate chamber 404 and coupled to gas exhaustlines 410 arranged on or within the structural housing 402. In someembodiments, the hot plate chamber 404 and/or hot plate 408 are coupledto hot plate chamber control circuitry 420 through wires 418 orwirelessly, and a motor (see, 602 of FIG. 15 ) is coupled to motorcontrol circuitry 606 through wires 603 or wirelessly.

As shown in cross-sectional view 1500 of FIG. 15 , in some embodiments,a motor 602 may be arranged within the hot plate chamber 404 and coupledto the hot plate 408. In some embodiments, the door (416 of FIG. 14 )hot plate chamber 404 may be closed, and a baking process may beperformed as controlled by the hot plate chamber control circuitry 420.In such embodiments, the motor control circuitry 606 may turn the motor602 “ON” to rotate 604 the motor 602, the hot plate 408, andsubsequently, the wafer 214 around an axis of rotation 610 that extendsthrough and is perpendicular to an upper surface of the hot plate 408.In such embodiments, the motor 602 is continuously rotated 604throughout the baking process. In some embodiments, the motor controlcircuitry 606 and the hot plate chamber control circuitry 420 worksimultaneously such that the wafer 214 is continuously spinning whilethe baking process is being conducted such that the wafer 214 isarranged at different orientations in the hot plate chamber 404throughout the baking process. This way, in such embodiments, gases 1502from the one or more solvents from the sol-gel solution layer 1302 maymore evenly exit out of the hot plate chamber 404 through the gas poreopenings 412. With a more even distribution of the removal of gases 1502from the hot plate chamber 404, the sol-gel solution layer 1302 may moreuniformly transform into a solid layer having a low variation incomposition throughout the wafer 214.

In some embodiments, the baking process comprises a drying step and adecomposition step. In some embodiments, the drying step may beperformed at a first temperature, and the decomposition step may beperformed at a second temperature greater than the first temperature.For example, in some embodiments, the drying step may be performed atthe first temperature in a range of between approximately 120 degreesCelsius and approximately 140 degrees Celsius, whereas the decompositionstep may be performed at the second temperature in a range of betweenapproximately 340 degrees Celsius and approximately 360 degrees Celsius.In some embodiments, during the drying step of the baking process,majority (e.g., greater than 50 percent) of the one or more solventsevaporate and exit the hot plate chamber 404 as gases 1502 through thegas pore openings 412. In some embodiments, after the drying process,the sol-gel solution layer 1302 may be described as a “gel-like”material having a liquid and solid phase. Then, in some embodiments,during the decomposition step of the baking process, the temperature ofthe hot plate 408 and/or the hot plate chamber 404 is increased to thesecond temperature to further dry, decompose, and densify the sol-gelsolution layer 1302 to form a first piezoelectric layer (see, 108 a ofFIG. 17 ) that is a solid layer arranged over the bottom electrode 106.Because of the continuous rotation 604 of the hot plate 408 by the motor602 while the hot plate 408 is at high temperatures, the resulting firstpiezoelectric layer (see, 108 a of FIG. 17 ) may have a reducedvariation in composition and thus, properties (e.g., breakdown voltage)throughout the first piezoelectric layer (see, 108 a of FIG. 17 ).

FIG. 16 illustrates a top-view 1600 of some embodiments corresponding tothe baking process of FIG. 15 , wherein the wafer 214 is continuouslyrotated 604.

As shown in the top-view 1600, in some embodiments, the wafer 214 isrotated at least a full 360-degree rotation during the baking process.In some embodiments, the wafer 214 is rotated a full 360-degree rotationmultiple times throughout the baking process to ensure an even exit ofgases (1502 of FIG. 15 ) from the hot plate chamber 404. In someembodiments, the motor control circuitry 606 controls the speed (e.g.,rotations per minute) of the motor (602 of FIG. 15 ). Further, in someembodiments, the notch 216 of the wafer 214 may be used to ensure thatthe wafer 214 is centered/aligned on the hot plate (408 of FIG. 15 ).

As shown in cross-sectional view 1700 of FIG. 17 , in some embodiments,after the baking process, a first piezoelectric layer 108 a is formedover the bottom electrode 106 on the wafer 214. In such embodiments, thefirst piezoelectric layer 108 a may have a first thickness t₁. In someembodiments, the first thickness t₁ is in a range of between, forexample, approximately 500 angstroms and approximately 3000 angstroms.In some embodiments, the first piezoelectric layer 108 a comprises apiezoelectric material such as, for example, lead zirconate titanate. Inother embodiments, the first piezoelectric layer 108 a may comprise someother piezoelectric material such as, for example, aluminum nitride,lithium niobate, gallium arsenide, zinc oxide, quartz single crystals,polymer-film piezoelectrics, or some other suitable piezoelectricmaterial. Because of the continuous rotation of the wafer 214 throughoutthe baking process, the first piezoelectric layer 108 a may have areduction in variation in composition throughout its area on the wafer214. In some embodiments, for example, a first area of the firstpiezoelectric layer 108 a may have a first concentration of a firstelement, whereas a second area of the first piezoelectric layer 108 amay have a second concentration of the first element that is differentthan the first concentration. However, because of the continuousrotation of the wafer 214 during the baking process, a differencebetween the first and second concentrations may be reduced. As a result,the first piezoelectric layer 108 a may have more uniform (i.e., lessvariation in) properties (e.g., breakdown voltage) throughout its areaon the wafer 214.

As shown in cross-sectional view 1800 of FIG. 18 , in some embodiments,the steps illustrated in FIGS. 10-17 are repeated several times toproduce a piezoelectric structure 108 comprising multiple piezoelectriclayers (e.g., 108 a-d). For example, in some embodiments, thepiezoelectric structure 108 may comprise a second piezoelectric layer108 b arranged over the first piezoelectric layer 108 a, a thirdpiezoelectric layer 108 c arranged over the second piezoelectric layer108 b, and a fourth piezoelectric layer 108 d arranged over the thirdpiezoelectric layer 108 c. In other embodiments, the piezoelectricstructure 108 may comprise more or less than the first through fourthpiezoelectric layers 108 a-d. Further, in some embodiments, thepiezoelectric structure 108 may comprise a same piezoelectric materialthroughout the first through fourth piezoelectric layers 108 a-d. Insome embodiments, the piezoelectric structure 108 may have a secondthickness t₂ in a range of between, for example, approximately 2,000angstroms and approximately 30,000 angstroms. Because each of the firstthrough fourth piezoelectric layers 108 a-d were formed to have areduced variation in composition by continuously rotating the hot plate(408 of FIG. 14 ) during baking processes, the overall piezoelectricstructure 108 may also have a reduced variation in composition and thus,a reduced variation in properties (e.g., breakdown voltage) therebyincreasing reliability of the piezoelectric structure 108.

FIG. 19 illustrates a flow diagram of some embodiments of a method 1900corresponding to FIGS. 8-18 .

While method 1900 is illustrated and described below as a series of actsor events, it will be appreciated that the illustrated ordering of suchacts or events are not to be interpreted in a limiting sense. Forexample, some acts may occur in different orders and/or concurrentlywith other acts or events apart from those illustrated and/or describedherein. In addition, not all illustrated acts may be required toimplement one or more aspects or embodiments of the description herein.Further, one or more of the acts depicted herein may be carried out inone or more separate acts and/or phases.

At act 1902, a sol-gel solution layer is formed on a wafer using aspin-coat tool. FIG. 13 illustrates a cross-sectional view 1300 of someembodiments corresponding to act 1902.

At act 1904, the wafer is transported from the spin-coat tool to a hotplate in a hot plate chamber. FIG. 14 illustrates a perspective view1400 of some embodiments corresponding to act 1904.

At act 1906, a baking process is performed in the hot plate chamber todry, decompose, and densify the sol-gel solution layer to form apiezoelectric layer over the wafer.

At act 1908, the hot plate is rotated during the performing of thebaking process to reduce composition variation and thus, variation inproperties throughout the piezoelectric layer. FIG. 15 illustrates across-sectional view 1500 of some embodiments corresponding to acts 1906and 1908.

FIGS. 20A-23 illustrate various views 2000A-2300 of some alternativeembodiments of a method of forming a piezoelectric structure on a waferby a sol-gel process using an orientor device in a hot plate chamber.Although FIGS. 20A-23 are described in relation to a method, it will beappreciated that the structures disclosed in FIGS. 20A-23 are notlimited to such a method, but instead may stand alone as structuresindependent of the method.

In some such alternative embodiments, a method of forming the firstpiezoelectric layer (108 a of FIG. 17 ) over the wafer 214 includes theformation of a sol-gel solution layer 1302 over a bottom electrode 106on a wafer 214 as illustrated in FIGS. 8-13 . Then, the method mayproceed from FIG. 13 to FIG. 20A.

As shown in perspective view 2000A of FIG. 20A, in some embodiments, thewafer 214 is transported from the spin-coat tool of FIG. 13 to a hotplate chamber 404 in FIG. 20A. The hot plate 408 may comprise a waferchuck configured to hold the wafer 214 and a heating element configuredto heat up the wafer chuck and the wafer 214. In some such embodiments,the hot plate chamber 404 may include an orientor device 310 arrangedwithin the hot plate chamber 404 and over the hot plate 408. Theorientor device 310 may comprise an optical image device and analignment device, in some embodiments. In some embodiments, the opticalimage device and the alignment device are arranged within the hot platechamber 404, whereas in other embodiments, one of the optical imagedevice or the alignment device of the orientor device 310 may bearranged outside of the hot plate chamber 404. Nevertheless, in someembodiments, the door 416 of the hot plate chamber 404 may be opened414, and the wafer 214 may be transported onto the hot plate 408 afterthe spin-coat process of FIGS. 11-13 .

FIG. 20B illustrates a top-view 2000B of some embodiments of the wafer214 in the hot plate chamber 404 corresponding to the perspective view2000A of FIG. 20A.

As shown in the top-view 2000B, in some embodiments, the notch 216 inthe wafer 214 may be arranged at some arbitrary position in the hotplate chamber 404. After the wafer 214 is arranged on the hot plate (408of FIG. 20A) of the hot plate chamber 404, the orientor controlcircuitry 312 is configured to operate the orientor device 310 toidentify the location of the notch 216 of the wafer 214. In someembodiments, the door 416 of the hot plate chamber 404 may be opened,whereas in other embodiments, the door 416 of the hot plate chamber 404may be closed while the orientor device 310 locates the notch 216. Insome embodiments, the orientor device 310 uses some type of opticalimage device (e.g., CCD image sensor, CMOS image sensor, ToF camera,etc.) to locate the notch 216 on the wafer 214.

As shown in top-view 2100 of FIG. 21 , the orientor control circuitry312 may be configured to use the alignment device of the orientor device310 to rotate 2102 the wafer such that the notch 216 is moved from itsarbitrary location 216 a to a first predetermined position 2104 withinthe hot plate chamber 404. In some embodiments, the alignment device ofthe orientor device 310 may comprise some type of rotational devicecoupled to the hot plate (408 of FIG. 20A) to rotate 2102 the hot plate(408 of FIG. 20A) to put the notch 216 at the first predeterminedposition 2104 within the hot plate chamber 404. In other embodiments,the alignment device of the orientor device 310 may comprise some typeof robotic arm configured to pick up and rotate 2102 the wafer 214 suchthat the notch is at the first predetermined position 2104. In suchembodiments, the robotic arm or alignment device of the orientor device310 may be arranged within the hot plate chamber 404, whereas in otherembodiments, the robotic arm or alignment device of the orientor device310 may be arranged outside of the hot plate chamber 404 such that thedoor 416 of the hot plate chamber 404 is opened to rotate 2102 the wafer214.

In some embodiments, the first predetermined position 2104 of the notch216 may be arranged directly across from the door 416 of the hot platechamber. In other embodiments, the first predetermined position 2104 ofthe notch 216 may be arranged at some other location than what isillustrated in the top-view 2100 of FIG. 21 . Nevertheless, in someembodiments, prior to performing a baking process, the orientor device310 within the hot plate chamber 404 may be used to orient the notch 216of the wafer 214 to be at the first predetermined position 2104 withinthe hot plate chamber 404.

As shown in perspective view 2200 of FIG. 22 , in some embodiments, thedoor 416 to the hot plate chamber 404 is closed 2202, and a first cycleof a baking process is performed within the hot plate chamber 404 ascontrolled by the hot plate chamber control circuitry 420. In suchembodiments, the first cycle of the baking process is performed whilethe notch 216 of the wafer 214 is arranged at the first predeterminedposition 2104 in the hot plate chamber 404. In some embodiments, thewafer 214 remains stationary while the first cycle of the baking processis performed. In some embodiments, the first cycle of the baking processincludes the drying step at the first temperature and the decompositionstep at the second temperature greater than the first temperature. Insome embodiments, during the first cycle of the baking process, gases1502 are released through the gas pore openings 412 and the gas exhaustlines 410. In some embodiments, during the first cycle of the bakingprocess, only a portion of the solvent in the sol-gel solution layer(1302 of FIG. 21 ) is evaporated. Thus, in some embodiments, a solidlayer comprising piezoelectric material is not yet formed after thefirst cycle of the baking process.

As shown in the top-view 2300 of FIG. 23 , in some embodiments, afterthe first cycle of the baking process, the orientor control circuitry312 may operate the orientor device 310 to again rotate 2102 the wafer214 and/or the hot plate (408 of FIG. 22 ) such that the notch 216 isarranged at a second predetermined position 2306 within the hot platechamber 404. In some embodiments, the door 416 of the hot plate chamber404 is opened to perform the rotation 2102, whereas in otherembodiments, the door 416 of the hot plate chamber 404 remains closed toperform the rotation 2102 after the first cycle of the baking process.In some embodiments, the wafer 214 and/or the hot plate (408 of FIG. 22) may be rotated 2102 a predetermined amount of degrees 2312 away fromthe first predetermined position 2104 to reach the second predeterminedposition 2306. In some embodiments, the predetermined amount of degrees2312 is defined as the angle between the first predetermined position2104 and the second predetermined position 2306, wherein the vertex ofthe angle is arranged at a center of the wafer 214. In some embodiments,the predetermined amount of degrees 2312 may be equal to approximately90 degrees. In other embodiments, the predetermined amount of degrees2312 may be in a range of between, for example, approximately 1 degreeand approximately 180 degrees.

Once the orientor device 310 rotates 2102 the wafer 214 such that thenotch 216 is arranged at the second predetermined position 2306, asecond cycle of the baking process may be performed, in someembodiments. In some embodiments, the second cycle of the baking processmay comprise the same parameters (e.g., time, temperature, pressure,etc.) as the first cycle of the baking process. In some embodiments,during the second cycle of the baking process, gases (1502 of FIG. 22 )are again released through the gas pore openings (412 of FIG. 22 ) andthe gas exhaust lines (410 of FIG. 22 ). In some embodiments, during thesecond cycle of the baking process, only a portion of the solvent in thesol-gel solution layer 1302 is evaporated. Thus, in some embodiments, asolid layer comprising piezoelectric material is not yet formed afterthe second cycle of the baking process. In other embodiments, a solidlayer comprising a piezoelectric material may be formed after the secondcycle of the baking process.

In some embodiments, after the second cycle of the baking process, theorientor device 310 may be configured to rotate the wafer 214 and/or thehot plate (408 of FIG. 22 ) the predetermined amount of degrees 2312such that the notch 216 of the wafer 214 is arranged at a thirdpredetermined position 2308 within the hot plate chamber 404. The thirdpredetermined position 2308 is arranged at the predetermined amount ofdegrees 2312 away from the second predetermined position 2306. Then, athird cycle of the baking process may be performed while the notch 216of the wafer 214 is arranged at the third predetermined position 2308within the hot plate chamber 404, in some embodiments.

In some embodiments, after the third cycle of the baking process, theorientor device 310 may be configured to rotate the wafer 214 and/or thehot plate (408 of FIG. 22 ) the predetermined amount of degrees 2312such that the notch 216 of the wafer 214 is arranged at a fourthpredetermined position 2310 within the hot plate chamber 404. The fourthpredetermined position 2310 is arranged at the predetermined amount ofdegrees 2312 away from the third predetermined position 2308. Then, afourth cycle of the baking process may be performed while the notch 216of the wafer 214 is arranged at the fourth predetermined position 2310within the hot plate chamber 404, in some embodiments.

In some embodiments, more or less than four cycles of the baking processmay be performed. Further, in some embodiments, each cycle of the bakingprocess may comprise the same parameters (e.g., time, temperature,pressure, etc.), whereas in some other embodiments, at least one of thecycles of the baking process may comprise different parameters (e.g.,time, temperature, pressure, etc.) than at least another cycle of thebaking process. In some embodiments, each cycle of the baking processmay comprise the drying step and the decomposition step. In some otherembodiments, the first through fourth cycles of the baking process maybe conducted at the parameters for the drying step of the bakingprocess, and then the first through fourth cycles of the baking processat the first through fourth predetermined positions, respectively, maybe repeated at the parameters for the decomposition step of the bakingprocess. In some embodiments, the number of cycles of the baking processperformed may be equal to 360 degrees divided by the predeterminedamount of degrees 2312. For example, in some embodiments, wherein thepredetermined amount of degrees 2312 equals about 90 degrees, fourcycles of the baking process may be performed.

In such embodiments wherein the wafer 214 is arranged at differentorientations (e.g., the first predetermined position 2104, the secondpredetermined position 2306, the third predetermined position 2308, thefourth predetermined position 2310) within the hot plate chamber 404throughout the baking process, gases (1502 of FIG. 22 ) from the sol-gelsolution layer 1302 may more evenly exit out of the hot plate chamber404 through the gas pore openings (412 of FIG. 22 ). With a more evendistribution of the removal of gases 1502 from the hot plate chamber404, the sol-gel solution layer 1302 may more uniformly transform into asolid layer (e.g., first piezoelectric layer 108 a of FIG. 107 ) havinga low variation in composition, and thus properties (e.g., breakdownvoltage) throughout the wafer 214.

In some embodiments, it will be appreciated that the method illustratedin FIGS. 8-13 and FIGS. 20A-23 may be repeated to form multiplepiezoelectric layers (e.g., the first through fourth piezoelectriclayers 108 a-d of FIG. 18 ) over the wafer 214.

FIG. 24 illustrates a flow diagram of some embodiments of a method 2400corresponding to FIGS. 20A-23 .

While method 2400 is illustrated and described below as a series of actsor events, it will be appreciated that the illustrated ordering of suchacts or events are not to be interpreted in a limiting sense. Forexample, some acts may occur in different orders and/or concurrentlywith other acts or events apart from those illustrated and/or describedherein. In addition, not all illustrated acts may be required toimplement one or more aspects or embodiments of the description herein.Further, one or more of the acts depicted herein may be carried out inone or more separate acts and/or phases.

At act 2402, a sol-gel solution layer is formed on a wafer using aspin-coat tool. FIGS. 11-13 illustrate cross-sectional views 1100-1300,respectively, of some embodiments corresponding to act 2402.

At act 2404, the wafer is transported from the spin-coat tool to a hotplate in a hot plate chamber. FIG. 20A illustrates a perspective view2000A of some embodiments corresponding to act 2404.

At act 2406, a location of a notch on the wafer is determined. FIG. 20Billustrates a top-view 2000B of some embodiments corresponding to act2406.

At act 2408, the wafer is oriented such that the notch is arranged at afirst predetermined position within the hot plate chamber. FIG. 21illustrates a top-view 2100 of some embodiments corresponding to act2408.

At act 2410, a first cycle of the baking process is performed to dry,decompose, and densify the sol-gel solution layer. FIG. 22 illustrates aperspective view 2200 of some embodiments corresponding to act 2410.

At act 2412, the wafer is oriented such that the notch is arranged at asecond predetermined position within the hot plate chamber by rotatingthe wafer a predetermined amount of degrees away from the firstpredetermined position.

At act 2414, a second cycle of the baking process is performed in thehot plate chamber to further dry, decompose, and densify the sol-gelsolution layer.

At act 2416, the wafer is oriented such that the notch is arranged at athird predetermined position within the hot plate chamber by rotatingthe wafer the predetermined amount of degrees away from the secondpredetermined position.

At act 2418, a third cycle of the baking process is performed in the hotplate chamber to further dry, decompose, and densify the sol-gelsolution layer.

At act 2420, the wafer is oriented such that the notch is arranged at afourth predetermined position within the hot plate chamber by rotatingthe wafer the predetermined amount of degrees away from the thirdpredetermined position.

At act 2422, a fourth cycle of the baking process is performed in thehot plate chamber to further dry, decompose, and densify the sol-gelsolution layer to form a piezoelectric layer over the wafer. FIG. 23illustrates a top-view 2300 of some embodiments corresponding to acts2412, 2414, 2416, 2418, 2420, and 2422.

FIGS. 25A-28 illustrate various views 2500A-2800 of some otheralternative embodiments of a method of forming a piezoelectric structureon a wafer by a sol-gel process using an orientor device in a spin-coattool. Although FIGS. 25A-28 are described in relation to a method, itwill be appreciated that the structures disclosed in FIGS. 25A-28 arenot limited to such a method, but instead may stand alone as structuresindependent of the method.

In some other alternative embodiments, a method of forming the firstpiezoelectric layer (108 a of FIG. 17 ) over the wafer 214 includes theformation of a sol-gel solution layer 1302 over a bottom electrode 106on a wafer 214 as illustrated in FIGS. 8-13 . Then, the method mayproceed from FIG. 13 to FIG. 25A.

As shown in cross-sectional view 2500A of FIG. 25A, in some embodiments,the orientor device 310 may be arranged within the spin-coat toolhousing 316 and over the wafer 214. In some such embodiments, theorientor device 310 may comprise an optical image device and analignment device arranged within the spin-coat tool housing 316, whereasin other embodiments, one of the optical image device or the alignmentdevice of the orientor device 310 may be arranged outside of thespin-coat tool housing 316. Nevertheless, in some embodiments, after theformation of the sol-gel solution layer 1302 on the bottom electrode106, the orientor control circuitry 312 may be used to analyze the wafer214, as illustrated by dotted lines 314, to locate the notch (216 ofFIG. 9 ) of the wafer 214.

FIG. 25B illustrates a top-view 2500B of some embodiments of the wafer214 after the spin-coat process. In the top-view 2500B of FIG. 25B, thenotch 216 of the wafer 214 may be arranged at some arbitrary locations,and located by the optical image device within the orientor device 310.

As shown in top-view 2600 of FIG. 26 , the orientor control circuitry312 may be configured to use the alignment device of the orientor device(310 of FIG. 25A) to rotate 2602 the wafer 214 such that the notch 216is moved from its arbitrary location 216 a to a first predeterminedposition 2104 within the spin-coat tool housing 316. In someembodiments, the alignment device of the orientor device 310 may be orcomprise a robotic arm 2604. In such embodiments, the robotic arm 2604may rotate 2606 from an original position 2604 p to orient the wafer 214such that the notch 216 is arranged at the first predetermined position2104. In other embodiments, the alignment device of the orientor device310 may comprise some type of rotation device coupled to the wafer chuck(304 of FIG. 25A), for example. Further, in some embodiments, thealignment device of the orientor device 310, such as the robotic arm2604 of FIG. 26 , may be arranged outside of the spin-coat tool housing316, and the spin-coat tool housing 316 is opened such that the roboticarm 2604 can rotate 2602 the wafer 214. In some other embodiments, thealignment device of the orientor device 310 may be arranged within thespin-coat tool housing 316.

As shown in FIG. 27A, in some embodiments, the alignment device of theorientor device 310 and/or some additional transportation device may beused to transport the wafer 214 from the spin-coat tool housing (316 ofFIG. 26 ) to the hot plate 408 within the hot plate chamber 404. In suchembodiments, the alignment device of the orientor device 310 and/or theadditional transportation device may maintain the alignment of the wafer214, such that the notch 216 of the wafer 214 is arranged at the firstpredetermined position 2104 within the hot plate chamber 404.

In some other embodiments, it will be appreciated that the orientordevice 310 may be a separate tool housing unit. For example, in someembodiments, after the spin-coat process, the wafer 214 may betransported into an orientor device housing (not shown), and theorientor device 310 within the orientor device housing may be configuredto locate and align the notch 216 of the wafer 214 to be arranged at thefirst predetermined position 2104. Then, in such other embodiments, thewafer 214 may be transported from the orientor device housing into thehot plate chamber 404 such that the notch 216 of the wafer 214 isarranged at the first predetermined position 2104 within the hot platechamber 404.

FIG. 27B illustrates a top-view 2700B of some embodiments of the notch216 of the wafer 214 arranged at the first predetermined position 2104within the hot plate chamber 404.

As shown in the top-view 2700B, in some embodiments, the firstpredetermined position 2104 of the notch 216 may be arranged directlyacross from the door 416 of the hot plate chamber 404. In otherembodiments, the first predetermined position 2104 of the notch 216 maybe arranged at some other location than what is illustrated in thetop-view 2700B of FIG. 27B. Nevertheless, in some embodiments, prior toperforming a baking process, the notch 216 of the wafer 214 is arrangedat the first predetermined position 2104 within the hot plate chamber404.

As shown in perspective view 2800 of FIG. 28 , in some embodiments, afirst cycle of the baking process may be performed in the hot platechamber 404 when the wafer 214 is arranged at the first predeterminedposition 2104 within the hot plate chamber 404. In some embodiments, thefirst cycle of the baking process may comprise the drying step and thedecomposition step. In some embodiments, the first cycle of the bakingprocess completely dries, decomposes, and densifies the sol-gel solutionlayer 1302 to form a first piezoelectric layer (108 a of FIG. 17 ). Insuch embodiments, the wafer 214 may remain stationary during the firstcycle of the baking process conducted at the first predeterminedposition 2104 within the hot plate chamber 404.

In some embodiments, the method of FIGS. 10-13 and FIGS. 25A-28 isrepeated to form multiple piezoelectric layers (e.g., the first throughfourth piezoelectric layers 108 a-d of FIG. 18 ) over the wafer, whereineach piezoelectric layer (e.g., 108 a-d of FIG. 18 ) undergoes a cycleof the baking process at a different predetermined location within thehot plate chamber 404. For example, in some embodiments, the method ofFIGS. 10-13 and FIGS. 25A-28 are repeated to form a second sol-gelsolution layer over the first piezoelectric layer (108 a of FIG. 17 ).Then, the orientor device 310 arranged within or outside of thespin-coat tool housing (316 of FIG. 25A) is used to orient the notch 216of the wafer 214 to be located at a second predetermined location (e.g.,2306 of FIG. 23 ). In such embodiments, a second cycle of the bakingprocess is then performed when the notch 216 of the wafer 214 isarranged at the second predetermined position 2306 within the hot platechamber 404. In some such embodiments, the second cycle of the bakingprocess may be completely dry, decompose, and densify the second sol-gelsolution layer to form a second piezoelectric layer (108 b of FIG. 18 )over the first piezoelectric layer (108 a of FIG. 18 ). In some suchembodiments, the method of FIGS. 10-13 and FIGS. 25A-28 are repeated athird time to form a third piezoelectric layer (108 c of FIG. 18 ) at athird predetermined position (2308 of FIG. 23 ), are repeated a fourthtime to form a fourth piezoelectric layer (108 d of FIG. 18 ) at afourth predetermined position (2310 of FIG. 23 ), and so on.

In such embodiments, the overall piezoelectric structure (108 of FIG. 18) may have a reduced variation in composition and thus, properties(e.g., breakdown voltage) because the baking process is performed atdifferent orientations within the hot plate chamber 404. However, insuch embodiments, wherein the method of FIGS. 10-13 and FIGS. 25A-28 areused to form a piezoelectric layer, each piezoelectric layer (108 a-d ofFIG. 18 ) may have a varying composition and varying properties (e.g.,breakdown voltage) throughout each piezoelectric layer because the wafer214 was not rotated throughout each the baking process as shown in themethod of FIGS. 15 and 16 or FIGS. 20A-23 , for example. Nevertheless,by forming the piezoelectric layers (e.g., 108 a-d of FIG. 18 ) atdifferent orientations (e.g., the first predetermined position 2104, thesecond predetermined position 2306, the third predetermined position2308, the fourth predetermined position 2310 of FIG. 23 ) within the hotplate chamber 404 as in FIGS. 10-13 and 25A-28 , the overallpiezoelectric structure (108 of FIG. 18 ) may have a reduced variationin composition and thus, properties (e.g., breakdown voltage).

FIG. 29 illustrates a flow diagram of some embodiments of a method 2900corresponding to FIGS. 25A-28 .

While method 2900 is illustrated and described below as a series of actsor events, it will be appreciated that the illustrated ordering of suchacts or events are not to be interpreted in a limiting sense. Forexample, some acts may occur in different orders and/or concurrentlywith other acts or events apart from those illustrated and/or describedherein. In addition, not all illustrated acts may be required toimplement one or more aspects or embodiments of the description herein.Further, one or more of the acts depicted herein may be carried out inone or more separate acts and/or phases.

At act 2902, a first sol-gel solution layer is formed on a wafer using aspin-coat tool. FIGS. 11-13 illustrate cross-sectional views 1100-1300,respectively, of some embodiments corresponding to act 2902.

At act 2904, a location of a notch on the wafer is determined. FIGS. 25Aand 25B illustrate cross-sectional view 2500A and top-view 2500B of someembodiments corresponding to act 2904.

At act 2906, the wafer is oriented such that the notch is arranged at afirst predetermined position. FIG. 26 illustrates a top-view 2600 ofsome embodiments corresponding to act 2906.

At act 2908, the wafer is transported from the spin-coat tool to a hotplate in a hot plate chamber such that the notch of the wafer is at thefirst predetermined position in the hot plate chamber. FIG. 27Aillustrates a perspective view 2700A of some embodiments correspondingto act 2908.

At act 2910, a first cycle of a baking process is performed in the hotplate chamber to dry, decompose, and densify the first sol-gel solutionlayer to form a first piezoelectric layer. FIG. 28 illustrates aperspective view 2800 of some embodiments corresponding to act 2910.

At act 2912, the wafer is transported back into the spin-coat tool, anda second sol-gel solution layer is formed on the first piezoelectriclayer using the spin-coat tool. FIGS. 11-13 illustrate cross-sectionalviews 1100-1300, respectively, of some embodiments corresponding to act2912.

At act 2914, a location of the notch on the wafer is determined. FIGS.25A and 25B illustrate cross-sectional view 2500A and top-view 2500B ofsome embodiments corresponding to act 2914.

At act 2916, the wafer is oriented such that the notch of the wafer isarranged at a second predetermined location which is arranged at apredetermined amount of degrees away from the first predeterminedposition. FIG. 26 illustrates a top-view 2600 of some embodimentscorresponding to act 2916.

At act 2918, the wafer is transported from the spin-coat tool to a hotplate in a hot plate chamber such that the notch of the wafer is at thesecond predetermined position in the hot plate chamber. FIG. 27Aillustrates a perspective view 2700A of some embodiments correspondingto act 2918.

At act 2920, a second cycle of a baking process is performed in the hotplate chamber to dry, decompose, and densify the second sol-gel solutionlayer to form a second piezoelectric layer on the first piezoelectriclayer. FIG. 28 illustrates a perspective view 2800 of some embodimentscorresponding to act 2920.

FIGS. 30-32 illustrate various views 3000-3200 of some embodiments of amethod of forming piezoelectric devices from a piezoelectric structureformed on a wafer, wherein the wafer is arranged at differentorientations during a baking process to form the piezoelectricstructure. Although FIGS. 30-32 are described in relation to a method,it will be appreciated that the structures disclosed in FIGS. 30-32 arenot limited to such a method, but instead may stand alone as structuresindependent of the method.

As shown in cross-sectional view 3000 of FIG. 30 , after the firstthrough fourth piezoelectric layers 108 a-d are formed over the wafer, atop electrode 110 may be formed over the piezoelectric structure 108. Insome embodiments, the top electrode 110 is formed directly on thepiezoelectric structure 108. In some embodiments, the top electrode 110may comprise, for example, copper, platinum, gold, silver, titanium,cobalt, titanium nitride, manganese, zinc, or some other suitableconductive material. In some embodiments, the top electrode 110 may beformed by way of a deposition process (e.g., PVD, CVD, PE-CVD, ALD,sputtering, etc.).

As shown in top-view 3100 of FIG. 31 , in some embodiments, the wafer214 comprises multiple die regions 218, and a dicing process thatutilizes a rotating blade and/or water will separate each die region 218to form multiple piezoelectric devices.

The top-view 3100 of FIG. 31 , like the top-view 200 of FIG. 2 ,illustrates that each die region 218 may correspond to a piezoelectricdevice having a breakdown voltage that corresponds to a low breakdownvoltage 204, a mid-breakdown voltage 206, or a high breakdown voltage208 as indicated by a diagonal-stripe pattern, a cross pattern, or aconcentric-circle pattern, respectively.

In some embodiments, an overall variation in the breakdown voltagesthroughout the piezoelectric structure (108 of FIG. 30 ) on the wafer214 may be quantified by a range of between a and d. The reliability ofthe piezoelectric structure (108 of FIG. 30 ) may be increased byreducing the range between a and d such that the piezoelectric structure(108 of FIG. 30 ) may be formed with a more uniform, and thus,predictable breakdown voltage for each die region 218. This way, eachpiezoelectric device has a known breakdown voltage such that the controlcircuitry (112 of FIG. 1 ) does not apply a voltage bias across thepiezoelectric structure (108 of FIG. 30 ) in a piezoelectric device thatexceeds the known breakdown voltage and irreversibly damage thepiezoelectric structure (108 of FIG. 30 ). In some embodiments, reducingthe range between a and d for the breakdown voltage of the piezoelectricstructure (108 of FIG. 30 ) is achieved by rotating the wafer 214 duringthe baking process of a sol-gel process used to form the piezoelectricstructure (108 of FIG. 30 ) which may be achieved by, for example, themethods illustrated in FIGS. 14-18 , FIGS. 20A-23 , or FIGS. 25A-28 .

As shown in cross-sectional view 3200 of FIG. 32 , in some embodiments,a removal process may be performed to form a first piezoelectric device3202, a second piezoelectric device 3204, and a third piezoelectricdevice 3206 over the wafer 214. In some embodiments, the removal processmay remove portions of the bottom electrode 106, the piezoelectricstructure 108, and the top electrode 110 by way of photolithography andremoval processes. In other embodiments, the removal process maycomprise a dicing process that utilizes a blade and/or water tocompletely separate the first, second, and third piezoelectric devices3202, 3204, 3206 from one another and thereby removing/cutting throughportions of the passivation layer 104 and the wafer 214. Nevertheless,in such embodiments, variation between the breakdown voltages of thefirst, second, and third piezoelectric devices 3202, 3204, 3206 isreduced (e.g., less than 10 volts) because the piezoelectric structure108 was formed by rotating the wafer 214 throughout a baking processused to form the piezoelectric structure 108. By having a reducedvariation in breakdown voltage (e.g., less than 10 volts), each of thefirst, second, and third piezoelectric devices 3202, 3204, 3206 are morereliable.

FIG. 33 illustrates a flow diagram of some embodiments of a method 3300of forming a piezoelectric device from a piezoelectric structure formedon a wafer by a sol-gel process, wherein the wafer is arranged atdifferent orientations during a baking process of the sol-gel process toreduce variation in breakdown voltages amongst resulting piezoelectricdevices.

While method 3300 is illustrated and described below as a series of actsor events, it will be appreciated that the illustrated ordering of suchacts or events are not to be interpreted in a limiting sense. Forexample, some acts may occur in different orders and/or concurrentlywith other acts or events apart from those illustrated and/or describedherein. In addition, not all illustrated acts may be required toimplement one or more aspects or embodiments of the description herein.Further, one or more of the acts depicted herein may be carried out inone or more separate acts and/or phases.

At act 3302, a bottom electrode is formed over a wafer. FIG. 8illustrates cross-sectional view 800 of some embodiments correspondingto act 3302.

At act 3304, the wafer is transported onto a cooling plate and a coolingprocess is performed on the wafer. FIG. 10 illustrates cross-sectionalview 1000 of some embodiments corresponding to act 3304.

At act 3306, a sol-gel solution layer is formed on the wafer using aspin-coat tool. FIGS. 11-13 illustrate cross-sectional views 1100-1300,respectively, of some embodiments corresponding to act 3306.

At act 3308, the wafer is transported from the spin-coat tool to a hotplate in a hot plate chamber. FIG. 14 illustrates perspective view 1400of some embodiments corresponding to act 3308.

At act 3310, a baking process is performed in the hot plate chamber todry, decompose and densify the sol-gel solution layer to form apiezoelectric layer over the wafer, wherein the wafer is rotated to beat different predetermined positions in the hot plate chamber during thebaking process. FIGS. 15 and 16 illustrates cross-sectional view 1500and top-view 1600, respectively, of some embodiments corresponding toact 3310.

At act 3312, a top electrode is formed over the piezoelectric layer.FIG. 30 illustrates cross-sectional view 3000 of some embodimentscorresponding to act 3312.

At act 3314, the wafer is diced to form multiple piezoelectric devices.FIG. 32 illustrates cross-sectional view 3200 of some embodimentscorresponding to act 3314.

Therefore, the present disclosure relates to a method of forming apiezoelectric structure by forming the piezoelectric layers of thepiezoelectric structure at different orientations within a hot platechamber throughout a baking process to reduce variation in compositionand thus, properties (e.g., breakdown voltage) of the piezoelectricstructure to ultimately form reliable piezoelectric devices.

Accordingly, in some embodiments, the present disclosure relates to aprocessing tool, comprising: a wafer chuck disposed within a hot platechamber and having an upper surface configured to hold a semiconductorwafer; a heating element disposed within the wafer chuck and configuredto increase a temperature of the wafer chuck; a motor coupled to thewafer chuck and configured to rotate the wafer chuck around an axis ofrotation extending through the upper surface of the wafer chuck; andcontrol circuitry coupled to the motor and configured to operate themotor to rotate the wafer chuck while the temperature of the wafer chuckis increased to form a piezoelectric layer from a sol-gel solution layeron the semiconductor wafer.

In other embodiments, the present disclosure relates to a methodcomprising: forming a bottom electrode on a wafer; transporting thewafer onto a cooling plate and performing a cooling process on thewafer; forming a first sol-gel solution layer on the wafer using aspin-coat tool; transporting the wafer from the spin-coat tool to a hotplate in a hot plate chamber; performing a baking process in the hotplate chamber to dry the first sol-gel solution layer to form a firstpiezoelectric layer from the first sol-gel solution layer; forming a topelectrode over the first piezoelectric layer; and dicing the wafer toform multiple piezoelectric devices from the wafer, wherein the wafer isarranged at different orientations with respect to the hot plate chamberthroughout the baking process.

In yet other embodiments, the present disclosure relates to a methodcomprising: forming a bottom electrode on a wafer; forming a firstpiezoelectric layer on the bottom electrode using a sol-gel process,wherein the sol-gel process comprises: forming a first sol-gel solutionlayer on the wafer using a spin-coat tool, transporting the wafer fromthe spin-coat tool to a hot plate in a hot plate chamber, and performinga baking process in the hot plate chamber to dry, decompose, and densifythe first sol-gel solution layer to form the first piezoelectric layeron the bottom electrode, wherein the wafer is rotated within the hotplate chamber during the baking process; forming a top electrode overthe first piezoelectric layer; and forming multiple piezoelectricdevices from the wafer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: forming a bottom electrodeon a substrate; forming a first piezoelectric layer on the bottomelectrode using a sol-gel process, wherein the sol-gel processcomprises: spin coating a first sol-gel solution layer on the substrate,providing the substrate to a hot plate in a hot plate chamber after thefirst sol-gel solution layer is on the substrate, performing a bakingprocess in the hot plate chamber to dry, decompose, and densify thefirst sol-gel solution layer to form the first piezoelectric layer onthe bottom electrode, identifying a location of a notch on the substratewhen the substrate is in the hot plate chamber, and rotating thesubstrate within the hot plate chamber so that the notch moves along aclosed circular path while being exposed to the baking process; andforming a top electrode over the first piezoelectric layer; and formingmultiple piezoelectric devices from the substrate.
 2. The method ofclaim 1, wherein the substrate is arranged at different orientationswith respect to the hot plate chamber throughout the baking process bycontinuously rotating the hot plate during the baking process.
 3. Themethod of claim 1, further comprising: transporting the substrate onto acooling plate and performing a cooling process on the substrate prior tospin coating the first sol-gel solution layer on the substrate.
 4. Themethod of claim 1, further comprising: orienting the substrate such thatthe notch is arranged at different stationary positions within the hotplate chamber during different cycles of the baking process.
 5. Themethod of claim 4, wherein the different stationary positions areapproximately 90 degrees apart from one another.
 6. The method of claim1, further comprising: spin coating the first sol-gel solution layer onthe substrate within a spin-coating tool; identifying the notch on thesubstrate using an orientor device when the substrate is in thespin-coating tool; orienting the substrate such that the notch isarranged at a first predetermined orientation; maintaining the substrateat the first predetermined orientation while transporting the substratefrom the spin-coating tool to the hot plate in the hot plate chamber;and performing a first cycle of the baking process when the substrate isat the first predetermined orientation to form the first piezoelectriclayer from the first sol-gel solution layer.
 7. The method of claim 1,further comprising: spin coating a second sol-gel solution layer on thefirst piezoelectric layer within a spin-coating tool; providing thesubstrate to the hot plate in the hot plate chamber after the secondsol-gel solution layer is on the first piezoelectric layer; performing asecond baking process in the hot plate chamber to dry, decompose, anddensify the second sol-gel solution layer to form a second piezoelectriclayer on the first piezoelectric layer, wherein the substrate is rotatedwithin the hot plate chamber during the second baking process; andforming the top electrode over the second piezoelectric layer.
 8. Themethod of claim 7, further comprising: transporting the substrate backinto the spin-coating tool after the baking process is completed;forming the second sol-gel solution layer on the first piezoelectriclayer; identifying the notch using an orientor device within thespin-coating tool; orienting the substrate such that the notch isarranged at a second predetermined position; transporting the substratefrom the spin-coating tool to the hot plate in the hot plate chamberwhile maintaining the substrate at the second predetermined position;and performing a second cycle of the baking process when the substrateis at the second predetermined position to form the second piezoelectriclayer from the second sol-gel solution layer.
 9. The method of claim 1,wherein a difference between a minimum breakdown voltage of the multiplepiezoelectric devices and a maximum breakdown voltage of the multiplepiezoelectric devices is in a range of between approximately 8 volts andapproximately 10 volts.
 10. A method comprising: forming a bottomelectrode on a substrate; forming a first piezoelectric layer on thebottom electrode using a sol-gel process, wherein the sol-gel processcomprises: spin coating a first sol-gel solution layer on the substrate,providing the substrate to a hot plate in a hot plate chamber after thefirst sol-gel solution layer is on the substrate, performing a bakingprocess in the hot plate chamber to dry, decompose, and densify thefirst sol-gel solution layer to form the first piezoelectric layer onthe bottom electrode, identifying a location of a notch on the substratewhen the substrate is in the hot plate chamber, and rotating thesubstrate over multiple full 360-degree rotations within the hot platechamber so that the notch moves along a closed circular path while beingexposed to the baking process; forming a top electrode directly onto thefirst piezoelectric layer; and forming multiple piezoelectric devicesfrom the substrate.
 11. The method of claim 10, wherein the substrate isrotated continuously within the hot plate chamber during the bakingprocess.
 12. The method of claim 10, wherein each of the multiplepiezoelectric devices has a breakdown voltage, and wherein a differencebetween a minimum breakdown voltage of the multiple piezoelectricdevices and a maximum breakdown voltage of the multiple piezoelectricdevices is at most equal to 10 volts.
 13. The method of claim 10,wherein the baking process comprises multiple cycles, wherein thesubstrate is rotated between each of the multiple cycles, and whereinthe substrate is stationary during each of the multiple cycles of thebaking process.
 14. The method of claim 13, wherein the substrate isrotated by 90 degrees between each of the multiple cycles of the bakingprocess, and wherein the baking process comprises four cycles.
 15. Themethod of claim 13, wherein the substrate is rotated using an orientordevice arranged within the hot plate chamber, and wherein the orientordevice comprises an optical image device and an alignment device. 16.The method of claim 13, wherein each of the multiple cycles of thebaking process comprises a drying step at a first temperature and a geldecomposition step at a second temperature greater than the firsttemperature.
 17. A method comprising: forming a bottom electrode on asubstrate; forming a first piezoelectric layer on the bottom electrodeusing a sol-gel process, wherein the sol-gel process comprises: spincoating a first sol-gel solution layer on the substrate, providing thesubstrate to a hot plate in a hot plate chamber after the first sol-gelsolution layer is on the substrate, performing a baking process in thehot plate chamber to dry, decompose, and densify the first sol-gelsolution layer to form the first piezoelectric layer on the bottomelectrode, wherein the baking process comprises a drying step at a firsttemperature and a gel decomposition step at a second temperature greaterthan the first temperature, identifying a location of a notch on thesubstrate when the substrate is in the hot plate chamber, and rotatingthe substrate within the hot plate chamber so that the notch moves alonga closed circular path while being exposed to the baking process;forming a top electrode over the first piezoelectric layer; and formingmultiple piezoelectric devices from the substrate.
 18. The method ofclaim 17, further comprising: rotating the substrate such that the notchis in a first predetermined position with respect to the hot platechamber during a first cycle of the baking process; and rotating thesubstrate by a predetermined amount of degrees to a second predeterminedposition, during a second cycle of the baking process that is separatefrom the first cycle of the baking process.
 19. The method of claim 17,wherein the baking process comprises a first cycle that includesperforming the drying step at the first temperature and performing thegel decomposition step at the second temperature.
 20. The method ofclaim 19, wherein the baking process further comprises a second cyclecomprising one or more same parameters as the first cycle of the bakingprocess.